Permanent-magnet synchronous electric motors in which a permanent magnet that functions as a magnetic field means is mounted to a rotor are known conventionally. However, in electric motors that are used in “electrically assisted turbochargers” in which the electric motor is disposed between a turbine and a compressor of an automotive supercharger, since high-speed rotation that exceeds 100,000 revolutions per minute is required, problems with magnet holding strength arise if conventional permanent magnet electric motors are used in these electric motors.
In consideration of these conditions, conventional magnetic inductor electric motors have been proposed in which a permanent magnet that functions as a magnetic field means are disposed on a stator, and a rotor is configured such that two rotor cores to which gearwheel-shaped magnetic saliency is applied are disposed so as to be lined up axially so as to be offset circumferentially by a pitch of half a pole (see Patent Literature 1, for example). Because these rotors are constituted only by iron members that have a simple shape, high resistant strength against centrifugal forces is obtained. Thus, conventional magnetic inductor electric motors are used in applications that require high-speed rotation such as electrically assisted turbochargers, electrically driven compressors, etc.